EPO compes with 2005 express so it gives u a 4 gb limitation per database, while 2008 r2 gives you a 10 GB limit per database so it would make sense to install it by hand. If you already have 2005 installed.. you can just create another database on that server.
Yeah the 4GB limitation I'm guessing though I would never reach with 50 PCs though. So the limitation not sure if it's a big deal for my environment. Performance gain in 2008 R2 once again probably not worth a consideration. The consideration I have is maybe at some point down the road 2005 will not be supported whereas 2008 R2 came out only like a year ago.